SOME UNDESCRIBED PHARMACOLOGICAL PROPERTIES OF BULBOCAPNIN

¹ From the Merck Institute of Therapeutic Research, Rahway, New Jersey

Bulbocapnin produces a pronounced peripheral vasodilatation which is most marked in the ear, the extremities and the kidney, while the effect on the intestinal circulation is only slight. The site of this action is peripheral; it is strongest after injection into the inferior mesenteric artery, while injection into the internal carotid causes practically no change in leg volume. In the isolated rabbit's ear the rate of perfusion is greatly increased after addition of bulbocapnin to the perfusion-fluid.

Since several of the bulbocapnin effects suggest parasympathetic stimulation, the influence of atropin injection or of cutting of the vagi upon the bulbocapnin action was investigated. Although it abolished such symptoms as salivation, defecation or miosis, it was without influence on the peripheral vasodilatation.

While repeated administration does not materially change the vascular action of bulbocapnin itself, it greatly influences the result of a subsequent adrenalin injection; the rise of the blood pressure becomes less steep and the peripheral vasoconstriction less pronounced. The vascular effects of pituitrin, however, are not influenced by a previous bulbocapnin administration.

The movements of the isolated intestine and of the intestine in situ are depressed by bulbocapnin.

The coagulation time of blood remains unchanged after injection of bulbocapnin even in large doses.

One of the most pronounced effects of bulbocapnin is the complete suppression of the vasoconstrictor reflexes regularly observed in rabbits' ears after sensory, thermal or mechanical stimulation.